Le Mans Fuel Filler - Get Your Fill

Sprucing up a C3 with a Le Mans–style fuel fillerIns and outs of replacing fuel filler

One of the most distinctive styling cues for the current batch of restomods is the roller-latch fuel filler. Although commonly known as the "Le Mans" filler, because of its extensive use on race cars that ran at the legendary Euro enduro, it also appeared on many high-performance street cars from the era. Witness, for example, the legendary 500-horsepower Baldwin-Motion Phase III GT Corvette, which came standard with a written 11-second guarantee; a host of dramatic visual elements such as fender flares and fixed headlights; and, yes, the racy, dome-like Le Mans fuel filler. Also note its appearance on the AC Cobra, as well as on the stunning powder-blue '69 C3 featured in a recent BFGoodrich ad.

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Initially, the Le Mans filler wasn't selected for aesthetics: It was used on race cars because it was easy--and therefore fast--to use. Simply pulling the spring-loaded latch backwards frees the lid to flip open for refueling, and closing it is as simple as smacking the cap back down. The latch automatically engages, locking it shut. There's none of the twisting and aligning of tabs that's required with ordinary gas caps.

The problem, though, has been finding a way to incorporate one into a C3 Corvette, especially considering the large gas cap of the early sharks. While the fillers have been available from suppliers of Cobra parts, fitting them involved fabricating a filler neck for the gas tank, and perhaps even (gasp) cutting fiberglass. For those who want to go this route, there's plenty of information on it online, including drawings to take to your machinist to get the parts made.

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The good news is that there's now a much simpler way. R&R Specialties, located in Huntsville, Tennessee, offers a drop-in Le Mans fuel filler for both early and later sharks. While the shark filler is relatively new--I think I saw it first at the Sevierville Corvette Expo a couple years ago--R&R, which does business under the name Mustalgia, has been in the operation since the late '70s. Founded around producing Le Mans fillers for Cobra kit cars, the business grew quickly, until it was selling to 30 or 40 different companies. After years of getting requests for fillers for Grand Sports and vintage race cars, Mustalgia finally relented and began making versions for the Corvette. The kit consists of two major components--the cap with its hinged base and latch, as well as the round base that mounts to the body--and comes with the four screws needed to install it.

While the Le Mans filler is a faithful reproduction of the originals, a few things have changed since the '70s, most of them having to do with how the caps are made. Originally investment cast, the aluminum filler is now made by die casting, which is both more precise and offers a less porous end result. For those unfamiliar with the two processes, investment casting (also known as the "lost wax" method), is where the mold is used to make a wax model of the end product--here, the domed cap itself--and that wax piece is dipped into a ceramic slurry that hardens around it. When enough of the ceramic has built up, the wax is melted out--"lost"--and then the molten metal is poured in. Once the metal hardens, the ceramic is broken off of the finished product. In essence, the mold is used to make another mold that's used to make the mold that makes the part you want.

In die casting, the mold makes the part. Period. It's more expensive, but the result is higher quality. In the case of the cap, that's also because the reduced porosity lets the product be brought to a higher shine when polished. The base to which the caps mounts, meanwhile, is CNC machined from a 6-inch bar of aluminum, also nicely polished. All of the work is done in the U.S.; most of it right there in Tennessee.

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The roller-latch "LeMans" fuel filler is one of few cosmetic additions that still looks "right" on a chrome-bumper car. Available from Mustalgia, this one mounts quickly and without modification.

1 The aluminum fuel filler comes carefully wrapped in bubble wrap and plastic to protect its beautiful high polish. It also comes with the mounting screws and a hex wrench. The only other tool you'll need is a Phillips screwdriver.

2 The fuel-cap part of the assembly is held onto its round base by a pair of small set screws located at the back of the cap, under the hinge.

3 Since putting something shiny on your gas tank runs the risk of attracting vandals, I added a locking gas cap from Mid America Motorworks. It's chrome-plated and comes with two keys.

4 The locking cap comes with a cork gasket, which is not attached. If you need it, use a ring of black RTV to permanently attach it.

5 Normally, I might feel bad about changing the factory fuel-filler door, since it has the crossed-flags emblem on it. But since a previous owner removed it when he had the car painted, I didn't worry about it.

6 To remove the fuel-filler door, open it and unscrew the four Phillips screws that hold it in place.

7 Once the screws are out, pull the door forward and remove it; you may find it easier to get out if you close it most of the way.

8 Once the door is out, you may want to clean around the opening prior to installing the new filler. Note the little metal tabs. Those are what the mounting screws go through, and you'll need to line up the holes on the new filler with them.

9 While the Mustalgia instructions don't say to do it, I think it's easier if you remove the cap from the base prior to installation. Set the base gently in place, being careful to line up the mounting holes with the tabs.

10 Use the included screws to affix the base. Because it's a little smaller than the recess into which it fits, start each of the four screws and then snug them up a little at a time, keeping the gap between the base and the recess consistent.

11 With the base in place, set the cap on it and rotate it to the proper position. You may find it easier to line up the cap with it open.

12 Using the included hex key, tighten the set screws to hold the cap in place on the base. It's easy to scratch your paint with the hex key if you're not careful, so either go very slowly, or cover the area under the key.

13 That's it. Even as large as the factory gas cap is on the early sharks, it will still go easily in and out of place, as will our equally large locking cap.

14 Because aluminum is soft, it will scratch easily, but a polish such as Blue Magic Metal Polish Cream will quickly restore its shine. Judicious use of a buffing wheel should take care of any deeper scratches.

Check out the exciting true story behind the original Corvette Grand Sports, why they were made, who designed them, and who built them. Also check out the story behind the Corvette SS Prototype! Exciting details and pictures at Vette Magazine. » Read More